JPH01221806A - Modulation mixing dielectric membrane and electroluminescence device and opticaldisk - Google Patents

Abstract

PURPOSE:To enhance membrane properties of breakdown electric field strength and thermal breakdown by changing the mixing ratio of membrane materials at a specific cycle along the direction of membrane thickness. CONSTITUTION:Material A is a material with low breakdown voltage, characterized in a high dielectric constant and propagation-type breakdown; material B is a material with high breakdown voltage, characterized in a low dielectric constant and self- repairing-type breakdown. The region (layer) containing a larger proportion of the material A has a feature of propagation-type breakdown. By making this region sufficiently thin and putting the resultant thin layer between the regions containing a larger proportion of the material B, the layer produced has a breakdown mode of self-repairing type. Then, the mixing ratio of the materials A and B is changed at a cycle of 5-300Angstrom along the direction of the membrane thickness. The application of the present means, the modulation mixing, to two or more materials, can yield an effect under the same concept as that obtained by the modulation mixing between propagation-type breakdown and self-repairing-type breakdown materials, so that thermal stability and breakdown electric field strength of the resultant membrane can increase.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a modulated mixed dielectric film, and in particular to a film structure of a dielectric film suitable for use in potential devices such as electroluminescence devices and optical disks. It is.

[Conventional technology]

For dielectric films, it is important for applications that they have a high dielectric constant and a high breakdown electric field strength, but generally the two are in a contradictory relationship. Therefore, S I Oz yTa20. of FIG. 1(b). As an improvement of the single film such as, there is a laminated structure film (JP-A-52-129296) shown in FIG. -224
No. 098).

[Problem to be solved by the invention]

However, even in the conventional mixed membrane structure, there is no consideration taken to take advantage of the differences in the fracture characteristics of the single materials used (if forced to separate them, they can be divided into self-healing fractures and propagating fractures, but their characteristics are relative). The improvement in breakdown electric field strength was insufficient.

An object of the present invention is to provide a modulated mixed dielectric film that has improved breakdown electric field strength and thermal breakdown characteristics by improving the mixed film structure, and an electroluminescent device and an optical disk to which this film is applied.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a modulated mixed dielectric film in which the mixing ratio of the film materials changes at a cycle of 5 to 300 in the film thickness direction, in a dielectric film manufactured using at least two types of materials. This is a proposal.

The film material is a combination of a material with a strong propagation type dielectric breakdown property and a material with a strong self-repair type dielectric breakdown property.

Specifically, 510B, YzOi, 5liN*t'S
rnz03 g T a205g T l 02g H
f 02t A Q20,, Z ro2. X-Ta0.
, X-NbO3°X-T x O3 (or metal).

The present invention also includes: The present invention proposes an electroluminescent device using a modulated mixed dielectric film having the above structure and components as at least a part of an insulating layer.

The present invention further proposes an optical disc using a modulated mixed dielectric film having the above structure and components as at least a part of a protective layer.

[Effect]

In FIG. 1(a) showing the concept of the structure of the modulated mixed dielectric film according to the present invention, material A is a high dielectric constant material with low breakdown voltage and propagation type breakdown, and material B is a low dielectric constant and self-healing type material. Use a material with high breakdown voltage. Then, although the region (layer) containing a large amount of material A has the characteristics of propagation-type fracture, this region is set sufficiently thin and is sandwiched with a region containing a large amount of material B, which has the characteristic of self-healing fracture. By doing so, the destruction mode of the entire membrane can be made self-repairing. This is the result of improved stability against heat that can destroy the membrane.

Up to this point, the explanation has been divided into two extremes: propagation type failure and self-healing type failure, but in actual failure, there are many materials that self-repair on the low voltage side and propagate type on the high voltage side. Since the breakdown electric field strength is determined by the voltage at which propagation type breakdown occurs, it is not necessarily accurate to classify materials into two types, and when comparing two materials, one is considered to have a more self-healing character. It can be considered a strong material. If a modulation mixing method is used for these two or more materials, the same conceptual effect as when modulating and mixing a propagating fracture material and a self-healing fracture material described above can be obtained, and thermal stability is achieved. The damage and breakdown electric field strength increases.

Now, in order to create a modulated mixed dielectric film, a film forming apparatus having two or more particle generation sources may be used, and methods such as sputtering, vapor deposition, MBE, and CVD may be used.

A simple example is one-person material deposition → simultaneous deposition of AB materials → B
Material deposition → AB material simultaneous deposition → A material deposition...
Adopt the following steps.

In addition, by implanting the upper film material into the lower film material by ion blasting or the like, a mixed film similar to the simultaneous film formation of AB materials in the above procedure can be created.

These modulation structures can be observed using cross-sectional TEM (transmission electron microscopy f
It can be confirmed by direct observation in i). Also.

If the thickness of each layer is 50 Å or more, it can be confirmed by SIMS (secondary ion mass spectrometry).

Furthermore, the modulation period does not need to be constant in the film, but depends on the application, type of material, film growth characteristics, etc.

Better characteristics can be achieved by changing the film period.

[Example] Next, an example of the modulated mixed dielectric film according to the present invention will be described with reference to FIG.

Figure 2 shows S i O, which has a strong self-repairing destructive character.

FIG. 3 is a diagram showing the relative permittivity and breakdown electric field strength of a film made of TiO□, which has a strong propagation-type destructive property, and TiO□. This film is made of Si
It was created by sputtering an O2 target and a Tie2 target alternately. The film thickness created at one time for Sio2 and Tie is calculated to be 9, 3, 30 and 1, respectively.
0 people, 60 people and 20 people, 150 people and 50 people, 300 people and 100 people, 1800 people and 600 people, total membrane 71 people.
The layers were stacked repeatedly until there were 5,000 people. In this case, due to the effect of implanting sputtered particles into the film, at the boundary between Sio and Tie2, 5io2-Tie,
A mixed layer of 10 to 20 people has been formed, and this layer is estimated to consist of about 10 to 20 people, based on measurements of the light absorption edge. As shown in FIG. 2, although the dielectric constant is almost constant, the breakdown electric field strength is improved in the region where the calculated thickness of the layer is less than 100 Å. This value is the breakdown electric field strength (
(arrow position on the left of the vertical axis in Figure 2). That is, 3
Characteristic improvements due to the modulation mixing effect are observed in films with a period of 00 Å or less. Note that if the modulation period thickness is made too thin, it will become similar to a conventional mixed film, so here the lower limit is set to 5 people.

The cross-sectional structure of an example of a thin film EL (electroluminescence) device to which this modulated mixed dielectric film is applied is shown in Fig. 3, where 1 is a glass substrate and 2 is a transparent conductive film (200 na + thickness).
, 3 is the first insulating layer (500na+thickness), 4 is the light emitting layer (Z
nS: 0.5 wt% Mn, 500 nm thick), 5 is the second insulating layer (500 nm thick), 6 is the back electrode (200 nm thick)
It is. The light emission start voltage and device breakdown voltage due to a 1kHz sine wave of an EL device in which a TiO□/Sin modulation mixed film whose characteristics are shown in FIG. 2 are applied to the first and second insulating films of this thin film EL device are In Figure 4, the white circle indicates the emission starting voltage.
The black circle is the element breakdown voltage, and the difference between these two is the drive voltage margin. In order to drive stably, it is necessary to increase this drive voltage margin, but as shown in Figure 4,
The driving voltage margin increases in the region of 300 person cycles or less.

FIG. 5 shows an example in which the modulation mixed film of the present invention is used as a protective layer of a magneto-optical disk.

A protective layer that sandwiches the recording layer of a magneto-optical disk from one or both sides is required to have a high refractive index, 9 mechanical strength, thermal stability, low thermal conductivity, and the like. Although a mixed insulating film is effective as this protective layer in the sense that it combines the advantages of a single film, thermal stability can be further improved by using the modulated mixed dielectric film of the present invention. FIG. 5 shows a cross-sectional structure of a rewritable optical disc. 10 is a polycarbonate substrate, 12 is GdT
bFe recording layer (50 nm thick), 11 is a protective layer (long thickness) to which a modulation mixed film according to the present invention is applied.

By sputtering, TiO□10 people (calculated) and Si
A modulated mixed film was created by alternately stacking 0.10 particles (according to calculation) and using the effect of the sputtered particles being implanted into the film. As a result, the high refractive index of TiO2 and the
, in addition to its excellent mechanical strength.

Furthermore, an improvement in thermal stability was observed.

〔Effect of the invention〕

According to the present invention, the breakdown electric field strength of a mixed dielectric film can be improved. Therefore, a high dielectric constant material, which is difficult to use because its breakdown electric field strength is too low, can be used as a new material by mixing it with a material having a high breakdown electric field strength. It is particularly effective for devices such as EL display elements that require an insulating film that has both a high dielectric constant and high breakdown electric field strength.

In order to demonstrate the specific effects, we investigated the relationship between the breakdown electric field strength and the total film thickness of a modulated mixed film (calculated, Ti0.10 - 8L0.30) created by sputtering7 and the mixed film (T
ie, :S1o2=1:3) The relationship 8 between breakdown electric field strength and film thickness is shown in FIG. The effect of the present invention is remarkable for two or more cycles.

[Brief explanation of the drawing]

FIG. 1 (a) shows the concept of the structure of the modulated mixed dielectric film according to the present invention, (b) shows the conventional single film, (C) shows the conventional laminated film, (
d) is a diagram showing a conventional mixed membrane, and Figure 2 is a Tie
, : SiO, = 1 : 3 A diagram showing the dielectric constant and breakdown electric field strength with respect to the modulation mixing period of a multi-layer mixed film by sputtering. Figure 3 is a diagram showing the cross-sectional structure of a thin film EL element. Figure 4 is a diagram showing the cross-sectional structure of a thin film EL element. Figure 3 shows the emission start voltage and device breakdown voltage when the modulated mixed dielectric film shown in Figure 2 is used as the insulating layer of the EL element, and Figure 51 shows the modulated mixed M dielectric film used as the protective layer. FIG. 6, which is a diagram showing an optical disk, is a diagram showing a comparison of the breakdown electric field strength of a modulated mixed dielectric film and a conventional mixed film. DESCRIPTION OF SYMBOLS 1... Glass substrate, 2... Transparent conductive film, 3... First insulating layer, 4... Light emitting layer, 5... Second insulating layer, 6...
... Back electrode, 7... Breakdown electric field strength of modulated mixed dielectric film, 8... Breakdown electric field strength of conventional mixed film, 10... Polycarbonate substrate, 11... Protective layer, 12-GdT
bFe recording layer.

Claims (5)

[Claims] 1. A modulated mixed dielectric film manufactured from at least two types of materials, characterized in that the mixing ratio of the film materials changes in a period of 5 to 300 Å in the film thickness direction. 2. 2. The modulated mixed dielectric film according to claim 1, wherein the film material is a combination of a material with a strong propagation type dielectric breakdown property and a material with a strong self-healing type dielectric breakdown property. . 3. The modulated mixed dielectric film according to claim 1 or 2, wherein the film material is SiO_2, Y_2O_3, Si_3N.
_4, Sm_2O_3, Ta_2O_5, TiO_2,
HfO_2, Al_2O_3, ZrO_2, X-TaO
A modulated mixed dielectric film comprising a combination of at least two of _3, X-NbO_3, and X-TiO_3 (where x is metal). 4. An electroluminescent device characterized in that the modulated mixed dielectric film according to claim 1, 2, or 3 is used as at least a part of an insulating layer. 5. An optical disk characterized in that the modulated mixed dielectric film according to claim 1, 2, or 3 is used as at least a part of a protective layer.